1. Field of the Invention
The present invention relates to a charging member for charging the surface of an electrophotographic photosensitive member as a member to be charged up to a predetermined potential by applying voltage, and a process cartridge and electrophotographic image forming apparatus (hereinafter referred to as an “electrophotographic apparatus”) using the charging member.
2. Description of the Related Art
Electrophotographic apparatuses often employ a contact charging method as a method of charging a surface of an electrophotographic photosensitive member, in which voltage is applied to a charging member disposed in contact with or in the vicinity of the surface of the electrophotographic photosensitive member to charge the surface of the electrophotographic photosensitive member. Here, examples of the voltage to be applied include only DC voltage or AC voltage superimposed onto DC voltage.
As a charging member used for the contact charging method, Japanese Patent Application Laid-Open No. 2010-134452 discloses a charging roller including a surface layer having protrusions derived from resin particles and protrusions derived from graphite particles on the surface of the surface layer wherein the number of the protrusions derived from a graphite particle having a positive distance between each protrusion derived from a graphite particle and a plane containing vertexes of three protrusions derived from the resin particles adjacent to the protrusion derived from a graphite particle is 80% or more of the total number of the protrusions derived from graphite particles. Japanese Patent Application Laid-Open No. 2010-134452 also discloses that the charging roller attains uniform charging potential of an electrophotographic photosensitive member to form a high-quality electrophotographic image.